Prepare for CocoaPod spec

I figured this deserves to be made into a CocoaPod. The easiest way is probably to just include it as a static library, so I've committed the built library here, with all modern architectures (armv7,7s,64,i386,x86_64).

It'd probably be better to have CocoaPods build from source, but I wanted to take the quick & easy route as a first pass…

Anyway, you don't have to merge it in, but just wanted you to be aware. :) Thanks for making open source software, @davepeck.